Control apparatus

ABSTRACT

A control assembly to operate a gas oven. The main burner receives gas from a solenoid valve energized by a thermoelectric generator through a main thermostat switch. In order to reduce the oven temperature to, e.g. 170* F. to keep the food warm after a timer has run down, the timer and a keep-warm thermostat operate two switches, respectively, to short circuit the solenoid or the thermoelectric generator periodically. The thermoelectric generator output is in the millivolt region. Thus, use of one or two additional, inexpensive, series switches in the circuit can make solenoid operation unreliable because of even moderate contact resistance. Even the use of expensive gold may not avoid the series switch problem. The control assembly disclosed herein avoids this problem by use of a disabling shunt instead of a series switch.

United States Patent [1 Saponara Aug. 28, 1973 1 CONTROL APPARATUSPrimary ExaminerWi1liam E. Wayner a h 9 [75] lnventor gteirnienickSaponara, C attanooga AnomwC Come" Remsen, Jr-

[73] Assignee: International Telephone and Telegraph Corporation, NewYork, [57] ABSTRACT N Y A control assembly to operate a gas oven. Themain Filed g 2 1971 burner receives gas froma solenoid valve energizedby a thermoelectric generator through a main thermostat switch. 1norderto reduce the oven temperature to, eg 170F. to keep the food warmafter a timer has run down, the timer and a keep-warm thermostat operate[52] Cl 236/15 236/46 236/75 two switches, respectively, to shortcircuit the solenoid 3 17/1335 or the thermoelectric generatorperiodically. The ther- [51] Int. Cl. F231] 5/10 moelectric generatorOutput is in he mmivoh region. [58] Field of Search 236/15 21 46 Thus,use of one or two additional, inexpensive, series 236/75; l0 switches inthe circuit can make solenoid operation unreliable because of evenmoderate contact resistance. [5 61 References cued Even the use ofexpensive gold may not avoid the series UNITED STATES PATENTS switchproblem. The control assembly disclosed herein 3,281,074 10/1966 Solomon2 236/46 D avoids this problem'by use of a disabling shunt instead3,571,659 3/1971 Anzai 317/16 of a series switch. 2,717,123 9/1955Hilgert et a1..... 236/75 2,902,221 9/1959 l-lajny 236/75 x 8 Claims,Drawing Figures 47 r L/ 1 flee/755m 776 M52440 'LEC TRIO 1 QCTU/QTOQGE/VEE/QTOQ 43 "0527? :5 sow/vow ,51? Y O, i W/ND/NG ,3 7 -Y I L T A 9 1THEEMOSTflT/C 1 L ACUATOB i CONTROL APPARATUS BACKGROUND OF THEINVENTION This invention relates to electrical devices for energizationby the output voltage of a thermoelectric generator including at least atherrnopile, and more particularly, to a control assembly to deenergizesuch a device without opening the circuit between the device and thethermocouple.

Although the device of the present invention will have considerableutility when used in connection with an oven for a gas range in whichfood is cooked, the invention is not limited to this or any otherapplication described herein. It will, thus, have other'usefulapplications.

In the past, a thermocouple has been connected in series with a mainthermostat switch and a gas valve solenoid which admits gas to the mainburnerof the oven of a gas range. Thus, the thermocouple supplies anexciting voltage for the solenoid inthe millivolt region.

It is also old in the art to automatically reduce oven temperature bythe use of a timer. Typically, the temperature is reduced to 170 F. tohold the food at serving temperature after it has cooked. However, ifattempts are made to do this electrically in a millivolt system byopening the circuit, additional series contacts must be used. Theaddition of additional series contact resistances can make the systemunreliable. The reliability problem can be alleviated to some extent bythe use of gold or platinum contacts but this adds expense.

SUMMARY on THE INVENTION In accordance with the device of the presentinvention, the above described and other disadvantages of the prior artare overcome by short circuiting a thermocouple or the load connectedthereto. In either case, the load is disabled. However, no disadvantagesare attendant upon the short circuiting of thethermoelectric generatoror the load.

By short circuiting, no extra pair of contacts are needed in series withthe thermoelectric generator. The available E.M.F., therefore, remainshigh because additional contact resistance is absent. Further,inexpensive shorting contacts may be employed because they need not begold or platinum.

The above-described and other advantages of the present invention willbe better understood from the following detailed description whenconsidered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings whichare to beregarded as merely illustrative:

FIG. 1 is a vertical sectional view through a gas oven;

FIG. 2 is a vertical sectional view of a portion of a thermostaticactuator;

FIG. 3 is a vertical sectional view of a portion-of another thermostaticactuator; g

FIG. 4 is a block diagram of one embodiment of the present invention;and

FIG. 5 is a block diagram of another embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, an oven is indicatedat having a housing 11. A pair of bulbs 12 and 13 are fixed insidehousing 1-1. A pair of tubes 14 and 15 are connected from bulbs 12 andl3, respectively. The interior of, tubes 14. and 15 lie in.communication with the interiors of bulbs'l2. and 13', respectively.Bulbs 12 and 13 are thus hollow. Bulbs 12: and I3 and tubes 14 and 15are filled with a thermally expansible liquid. The manner in which bulbs12 and 13 are used will be described hereinafter.

A partition 16 is fixed inside oven 10 to housing 11. A main burner 17is also fixed inside housing 11. A solenoid valve 18 having a winding 19shown in FIGS. 4 and. 5 is connected from a gas input conduit 20 at apipe T 21. Inlet 20 is also connected to a pilot burner 22. A

thermoelectric generator 23 is located adjacent pilot burner 22 to beheated by the heat of combustion generated by gas burning at pilotburner 22.

It is not conventional to employ two bulbs 12 and 13 and two tubes 14and 15 in FIG. 1. However, all of the apparatus shown in FIG. 1, exceptthe two bulbs 12 and 13, and the two tubes 14 and 15 may be entirelyconventional.

Thermostats are shown at 24 and 25 in FIGS. 4 and 5. Thermostat 24includes bulb l2, tube 14, and all the structure other than tube 14,shown in FIG. 2. Note will be taken that tube 14 is connected to abellows 26 which operates a lever 27 biased by a spring 28. Lever 27 isfulcrumed on the end of a shaft 29, threaded through a housing 30. Therotatable position of shaft 29 is manually adjustable by a knob 31.

Repeated expansion and contraction of bellows 26 will cause repeatedopening of leaf spring contacts 32 and '33 of a switch 34 whenitheliquid in bulb 12 expands and contracts, respectively.

Bulb 12, tube 14 and all of the structure shown in FIG. 2 may beentirely conventional. The cooking temperature of the oven 10 may thusbeset by turning knob 31 from zero to some baking temperature.

Thermostat 25 operates differently from thermostat 24. Thermostat 25includes bulb l3, tube 15 and all the structure connected from tube 15,shown in FIG. 3. Thermostat 25 includes a bellows 35, a lever 36 and aspring 37 which may be, if desired, identical to bellows 26, lever 27and spring 28. A set screw 38 is threaded through housing 39 to set thekeep warm temperature of the oven.

The apparatus of FIG. 3 includes a switch 40 having leaf spring contacts41 and 42 which are engaged when bellows 35 expands. Thus, switch 40closes .when bellows 35 expands, whereas switch 34 opens when bellows 26expands.

As shown in FIG. 4, all of the structure of thermostat 24 is labeledthermostatic actuator" at 43, with the exception of switch 34.Similarly, all of the structure of thermostat 25 is labeled thermostaticactuator" 44, with the exception of switch 40.

Thermoelectric generator 23 has one lead 45 connected to ground at 46,and another lead 47 connected to switch 34. 1

Winding 19 has one lead 48-connected to ground at 46, and another lead49 connected to a junction 50. Junction 50 is connected to both switch34 and to a timer switch 51, timer switch 51 being operated by a timer52.

The timer switch 51, in turn, is connected to thermostat switch 40, theother side of thermostat switch 40 being grounded at 53.

In the embodiment of FIG. 4, timer 52 is of the type that keeps switch51 open until it runs down to time ZERO. Switch 51 is then closed. Timer52 is also of the type which may be located from a ZERO position to anOFF position where switch 51 is open to turn the keep warm control off.

In the operation of the embodiment of FIG. 4, knob 31 is turned to thedesired cooking temperature. Actuator 43 then closes switch 34 until thetemperature inside housing ll rises to the temperature set by turningknob 31. When the housing temperature rises above the set temperature,actuator 43 opens switch 34. When the temperature inside housing 11falls below the set temperature, actuator 43 closes switch 34, and soon. The foregoing is the operation with the timer 52 in the OFFposition. Should it be desired to bake at the set temperature for apredetermined time and then to reduce the temperature inside housing 11to, for example, 170 F., timer 52 is set to the baking time. Switch 51is thus kept open and baking occurs as previously described until thetimer 52 returns to the ZERO position. Switch 51 is then closed. Theactuator 44 has previously closed switch 40. The closure of switch 40short circuits winding 19 through switch 51 to ground. Thermostat 25thus acts as an override and lowers the temperature inside housing 11to, for example, 170 F. When the temperature inside housing 11 fallsbelow 170 F., the liquid inside bellows 35 will contract sufficiently toopen switch 40 and remove the short circuit across winding 19.Thermostat 25 will thus keep the temperature inside oven 11 at, forexample, 170 F. until timer 52 is turned to the OFF position.

As shown in FIG. 5, it is unnecessary to. have a ground connection.Winding lead48 may thus be connected to thermostat 25 by a lead 54,thermoelectric generator lead 45 being connected to both leads 48 and S4at a junction 55.

Although timer 52 may be entirely conventional, a timer 56 may also beemployed of a simpler nature, timer 56 also being conventional. Timer56. need not have an OFF position spaced from a ZERO position, asdescribed previously, in connection with timer 52. In this case, asingle-pole, double-throw switch 57 is connected from junction 50through a switch 48 operated by timer 56 to thermostat 25. Thus, to shutoff the keep warm, switch 57 is opened by switching to the manualposition. Timer 56 thus keeps switch 58 open at all times except when itis in the ZERO position. In the ZERO position, timer 56 closes switch58.

Both of the embodiments shown in FIGS. 4 and are employed to shortcircuit winding 19. However, this is not necessary. That is, theinvention may be practiced also by simply short circuitingthermoelectric generator 23.

Note will be taken that switches 34, 51, 40, 57 and 58 may either bemechanical, solid state or other switches. That is, the same or similarreferences to stable states" herein and in the claims is hereby definedto include mechanical and/or electrical stable states.

What is claimed is:

I. An oven comprising: a housing; a pilot burner fixed in said housing;a main burner fixed in said housing adjacent said pilot burner;thermoelectric generator means fixed in said housing in a positionadjacent said pilot burner and in a position to be heated by combustionof fuel emanating from said pilot burner, said thermoelectric generatormeans having first and second leads connected therefrom; a solenoidvalve having a fuel inlet, a fuel outlet and electromagnetic windingmeans, said winding means having first and second leads connectedtherefrom, said valve outlet being connected to said main burner tosupply fuel to said main burner for combustion thereat; a firstthermostat including a first thermostatic actuator having at least afirst device supported in said housing to produce an output inaccordance with the temperature therein, at least a first switch havingfirst and second contacts, said first thermostatic actuator having anarrangement connected from said first device to open said first switchwhen the temperature of the air inside said housing rises above apredetermined temperature and to close said first switch when thehousing temperature falls below said first predetermined temperature,said winding means second lead being connected to said thermoelectricgenerator means first lead, said thermoelectric generator means secondlead being connected to said first switch first contact, said firstswitch second contact being connected to said winding means first lead;and apparatus including a circuit connected in parallel with one of saidthermoelectric generator means and said electromagnetic winding means,said apparatus being actuatable to short circuit such means.

2. The invention as defined in claim 1, wherein said apparatus includesa second thermostat including a second thermostatic actuator having atleast a second device supported in said housing to produce an output inaccordance with the temperature therein, said second thermostatincluding at least a second switch having third and fourth contacts,said second actuator having an arrangement connected from said seconddevice to close said second switch when the housing temperature risesabove a second predetermined temperature and to open said second switchwhen the housing temperature falls below said second predeterminedtemperature, said second switch being connected in shunt with said onemeans.

3. The invention as defined in claim 2, including a timer having aswitch connected in series with said second switch from one lead of saidone means to the other lead thereof, said timer switch being open untilsaid timer runs down, whereupon it is closed.

4. The invention as defined in claim 3, wherein said timer is of thetype which may be set to a stationary OFF position spaced from its rundown or ZERO position, said timer switch being open when said timer isset to said OFF position.

5. The invention as defined in claim 4, wherein said first switchcontacts are plated with one of the metals gold and platinum, saidsecond switch contacts being free of gold and platinum, said one meansbeing said windingmeans, said first predetermined temperature beinghigher than said second predetermined temperature.

6. The invention as defined in claim 3, including an auxiliarysingle-pole, double-throw switch connected in series with said secondswitch from one lead of said-one means to the other lead thereof.

7. The invention as defined in claim 6, wherein said first switchcontacts are plated with one of the metals gold and platinum, saidsecond switch contacts being free of gold and platinum, said one meansbeing said winding means, said first predetermined temperature beinghigher than said second predetermined tempera- .ture.

8. An oven comprising: a housing; a pilot burner fixed in said housing;a main burner fixed in said housing adjacent said pilot burner;theremoelectric generator means fixed in said housing in a positionadjacent said pilot burner and in a position to be heated by combustionof fuel emanating from said pilot burner; a solenoid valve having a fuelinlet, a fuel outlet and electromagnetic winding means, said valveoutlet being connected to said main burner to supply fuel thereto forcombustion thereat; a first switch having an open position and a closedposition connected with both of said means and operable to cause saidwinding means to be energized by said thermoelectric generator means andto be deenergized; a series circuit connected in parallel with one ofsaid means, said circuit including a series connected second switchoperable between open and closed positions, said circuit being adaptedto short circuit said one means when said second switch is closed; andtemperature sensitive apparatus having connecting portions mountedinside and outside said housing connected to both of said switches foroperating the same, said apparatus causing said first switch to changeto one of said positions thereof when the temperature in said housingfalls below a first predetermined set temperature and to change to theother position thereof .when

mined set temperature and causing said second switch to move to its openposition when the temperature in said housing falls below said secondtemperature, said circuit also including a third switch connected inseries with said second switch, said third switch, when closed, enablingsaid second switch, when closed, to short circuit said one means, saidthird switch, when open, preventing said second switch, when closed,from short circuiting said one means, said first temperature beinghigher than said second temperature, closure of said second switch whilesaid third switch is closed short circuiting said one means andoverriding said first switch when said first switch is operated toenergize said winding means.

1. An oven comprising: a housing; a pilot burner fixed in said housing;a main burner fixed in said housing adjacent said pilot burner;thermoelectric generator means fixed in said housing in a positionadjacent said pilot burner and in a position to be heated by combustionof fuel emanating from said pilot burner, said thermoelectric generatormeans having first and second leads connected therefrom; a solenoidvalve having a fuel inlet, a fuel outlet and electromagnetic windingmeans, said winding means having first and second leads connectedtherefrom, said valve outlet being connected to said main burner tosupply fuel to said main burner for combustion thereat; a firstthermostat including a first thermostatic actuator having at least afirst device supported in said housing to produce an output inaccordance with the temperature therein, at least a first switch havingfirst and second contacts, said first thermostatic actuator having anarrangement connected from said first device to open said first switchwhen the temperature of the air inside said housing rises above apredetermined temperature and to close said first switch whEn thehousing temperature falls below said first predetermined temperature,said winding means second lead being connected to said thermoelectricgenerator means first lead, said thermoelectric generator means secondlead being connected to said first switch first contact, said firstswitch second contact being connected to said winding means first lead;and apparatus including a circuit connected in parallel with one of saidthermoelectric generator means and said electromagnetic winding means,said apparatus being actuatable to short circuit such means.
 2. Theinvention as defined in claim 1, wherein said apparatus includes asecond thermostat including a second thermostatic actuator having atleast a second device supported in said housing to produce an output inaccordance with the temperature therein, said second thermostatincluding at least a second switch having third and fourth contacts,said second actuator having an arrangement connected from said seconddevice to close said second switch when the housing temperature risesabove a second predetermined temperature and to open said second switchwhen the housing temperature falls below said second predeterminedtemperature, said second switch being connected in shunt with said onemeans.
 3. The invention as defined in claim 2, including a timer havinga switch connected in series with said second switch from one lead ofsaid one means to the other lead thereof, said timer switch being openuntil said timer runs down, whereupon it is closed.
 4. The invention asdefined in claim 3, wherein said timer is of the type which may be setto a stationary OFF position spaced from its run down or ZERO position,said timer switch being open when said timer is set to said OFFposition.
 5. The invention as defined in claim 4, wherein said firstswitch contacts are plated with one of the metals gold and platinum,said second switch contacts being free of gold and platinum, said onemeans being said winding means, said first predetermined temperaturebeing higher than said second predetermined temperature.
 6. Theinvention as defined in claim 3, including an auxiliary single-pole,double-throw switch connected in series with said second switch from onelead of said one means to the other lead thereof.
 7. The invention asdefined in claim 6, wherein said first switch contacts are plated withone of the metals gold and platinum, said second switch contacts beingfree of gold and platinum, said one means being said winding means, saidfirst predetermined temperature being higher than said secondpredetermined temperature.
 8. An oven comprising: a housing; a pilotburner fixed in said housing; a main burner fixed in said housingadjacent said pilot burner; theremoelectric generator means fixed insaid housing in a position adjacent said pilot burner and in a positionto be heated by combustion of fuel emanating from said pilot burner; asolenoid valve having a fuel inlet, a fuel outlet and electromagneticwinding means, said valve outlet being connected to said main burner tosupply fuel thereto for combustion thereat; a first switch having anopen position and a closed position connected with both of said meansand operable to cause said winding means to be energized by saidthermoelectric generator means and to be deenergized; a series circuitconnected in parallel with one of said means, said circuit including aseries connected second switch operable between open and closedpositions, said circuit being adapted to short circuit said one meanswhen said second switch is closed; and temperature sensitive apparatushaving connecting portions mounted inside and outside said housingconnected to both of said switches for operating the same, saidapparatus causing said first switch to change to one of said positionsthereof when the temperature in said housing falls below a firstpredetermined set temperature and to change to the other positionthereof when the temperature in said housing rises above saId firsttemperature, said valve supplying fuel to said main burner when saidfirst switch is in said one position thereof, said valve cutting off thesupply of fuel to said main burner when said first switch is in the saidother position thereof, said apparatus also causing said second switchto move to its closed position when the temperature in said housingrises above a second predetermined set temperature and causing saidsecond switch to move to its open position when the temperature in saidhousing falls below said second temperature, said circuit also includinga third switch connected in series with said second switch, said thirdswitch, when closed, enabling said second switch, when closed, to shortcircuit said one means, said third switch, when open, preventing saidsecond switch, when closed, from short circuiting said one means, saidfirst temperature being higher than said second temperature, closure ofsaid second switch while said third switch is closed short circuitingsaid one means and overriding said first switch when said first switchis operated to energize said winding means.